Last updated: 9th Apr 2019
Pricewise Insulation, a national insulation supplier, defines the two different kinds of wall insulation:
- Thermal wall insulation – installed in the external walls
- Acoustic wall insulation – installed in the internal walls
As the name suggests, the main purpose of thermal wall insulation is to minimise the transfer of heat and cold from the outside into the home. It should be installed between the vertical studs of all walls (including walls adjoining the garage) that are in direct contact with outside air, and it should be done prior to putting the wall lining in place.
On the other hand, acoustic wall insulation is specifically designed to hinder the transfer of airborne sound between rooms within the house. It is usually installed in the walls between bedrooms, bathrooms, laundries, and other areas where outside noise (such as traffic noise) is expected to cause problems.
It’s rare for wall insulation to be installed into existing homes. This is because the cost of removing the wall lining and replacing it again will be much higher than any energy savings that might be gained from the additional insulation – at least in the short to medium term.
The price of wall insulation
The cost of thermal wall insulation will be determined by two factors: the R-Value of the insulation batts and the spacing between the wall studs. If a standard R1.5 (this is around 75mm thick and is suitable for most jobs) is used and your wall studs are evenly spaced at 60cm, you can expect to pay between $5/m2 and $6/m2 for the job. This will cover the installation as well as the materials.
Meanwhile, acoustic wall insulation rates start at around $8/m2. This involves using R2.0 high-density acoustic insulation. Although mainly used for internal walls, it’s not uncommon for builders to prioritise acoustic wall insulation in some external walls of the home.
In order to calculate the total square metre area of a wall, simply multiply the height and width of the wall and then deduct the total area (height multiplied by width) of any windows and doors if necessary.
Important things to know
Insulation companies generally quote on a per-square metre basis for supply and installation jobs. This way, homeowners as well as builders are able to know for certain what the final cost will be. It also works as an incentive for installers to work as efficiently as possible.
You will need to prepare extra cash if your vertical walls studs are not evenly spaced. In cases like this, installers will need to do a lot of manual cutting work, and they will likely charge more for it.
Installing wall insulation is not a very difficult task in itself. It’s a matter of placing the pre-cut insulation batts between the wall studs to guarantee a secure fit. You can take a big step towards reducing the cost of your wall insulation project by making sure that the area to be insulated can be easily accessed by the installers and that the framing is built to proper standards.
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